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A007882

Number of lattice points inside circle of radius n is 4(a(n)+n)-3.

0, 1, 4, 8, 13, 22, 30, 41, 54, 67, 83, 98, 117, 139, 160, 183, 206, 234, 263, 292, 322, 357, 390, 424, 461, 502, 545, 585, 626, 673, 719, 770, 819, 870, 926, 977, 1034, 1090, 1153, 1214, 1272, 1339, 1404, 1475, 1543, 1610, 1683, 1755, 1832, 1907, 1990, 2070, 2147

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,3

COMMENTS

Number of ordered pairs of integers (x, y) such that x^2+y^2 < n^2 with x, y > 0. - Arkadiusz Wesolowski, Nov 13 2017

REFERENCES

R. K. Guy, Unsolved Problems in Number Theory, F1.

LINKS

Table of n, a(n) for n=1..53.

PROG

(Haskell)

a007882 n = length [(x, y) | x <- [1..n], y <- [1..n], x^2 + y^2 < n^2]